Bay Area flu hospitalizations surge 20-fold since mid-September, season's first death reported
With test positivity near 10% — the highest in California — and wastewater signals rising across four cities, the Bay Area is weeks ahead of its usual flu timeline.
San Francisco recorded its first flu-related death of the season this week — a milestone that in each of the two prior years didn't arrive until December. Flu hospitalizations in the city have climbed to 2.39 per 100,000 residents, up from just 0.12 per 100,000 in mid-September, a roughly 20-fold jump in a matter of weeks, according to SFGate.
The Bay Area has become California's leading flu hotspot, with test positivity approaching 10 percent — the highest rate in the state, according to California Department of Public Health data released Friday. Wastewater surveillance from WastewaterSCAN shows high flu levels in San Francisco, Palo Alto, Redwood City, and San Jose.
Once it starts, it's game on.— Dr. Matt Willis, former Marin County health officer
That warning captures the central concern among public health experts: seasonal flu, once it gains momentum, tends to keep climbing. The worry this year is that it has gained that momentum unusually early. In 2024 and 2025, San Francisco's hospitalization rates didn't reach their seasonal highs until December. The current surge is arriving in early October.
Gandhi noted she was surprised by a fatality this early. She added that vaccines are only now rolling out and that flu activity typically climbs in November or December, making the early death and hospitalization spike notable. COVID-19 activity also remains elevated in the region, meaning Bay Area residents are navigating two concurrent respiratory threats heading into fall.
Experts emphasize the story here is timing, not a fundamentally new pattern. Seasonal flu always spreads — the concern is that a head start in October, before vaccination rates have built up, could mean a longer or more intense season overall. California tracks flu hospitalizations, test positivity, emergency department visits, and wastewater levels through its Respiratory Virus Dashboard, which pulls lab data via the state's electronic reporting system.
Why it matters — An early flu surge — arriving weeks ahead of schedule and before vaccination has widely taken hold — means Bay Area residents face a potentially longer season with less immunity in place to blunt it.
⚠ Not yet confirmed
- Flu activity is expected to continue climbing through the fall.
- direct quote from Dr. Monica Gandhi
Reported by sfgate.com, sftimes.com, data.chhs.ca.gov
